Typical iron club heads are solid with a flat hitting face and generally either muscle back and cavity back clubs. Traditionally all irons were muscle back, which are smooth at the back with low offset, thin topline and thin sole. Cavity back irons have a hollowed out back and the club head mass is redistributed to the sole and the perimeter of the club head, which moves the center of gravity lower to the ground and rearward making the iron launch the ball higher, and increases rotational moment of inertia thereby lowering its tendency to rotate on mis-hits and enlarging the sweet spot.
Some muscle back irons have an interior hollow section, such that the club resembles a muscle back on the outside but the interior hollow section alters the club's mass characteristics. One example is U.S. Pat. No. 4,645,207 to Teramoto et al. The Teramoto patent discloses a set of iron golf clubs in which the iron club is cast by the lost wax method, and the back member is welded at the back of the face member to form a hollow section between the back and face members. As the club changes from a longer iron to a shorter iron, the hollow section is gradually decreased to zero and the sole width is gradually decreased. No support is provided to the hitting face.
Another example is U.S. Pat. No. 4,754,969 to Kobayashi. The Kobayashi patent discloses a set of golf clubs wherein each one-piece club head includes a hollow section behind the striking face. Each of the club heads is made of a stainless steel by, for example, a lost wax casting process. The material of each of the face portions of the club heads is then annealed to increase its elasticity. The striking face is thinner for long irons, but no support is provided to the hitting face.
Another example is U.S. Pat. No. 7,126,339 to Nagai et al., which discloses utility golf clubs, which generally include a hollow interior.
There remains a need in the art for an improved iron-type golf club.